Method of making ferroconcrete reinforcing elements



Oct. 28, 1941. HOFFMAN 'Z',Z60,779

METHOD OF MAKING FERROCONCRETE IREINFORCING ELEMENTS Filed Oct. 27, 1938 I'm enter fwd W Patented Oct. 28, 1 941 warrior) or MAKING manoconcnara' REINFORCING ELEMENTS Ernst Hcflmann, Vienna, Germany ripplication October 27, 1938, Serial No. 237,325 In Austria October 28, 1937 6 Claims.

This invention relates to ferro-concrete reinforcement elements, and to the manufacturing thereof.

It is known that the strength of reinforcing elements for concrete structures can be increased, thus permitting of higher loads being applied thereto, by subjecting the reinforcing rods to cold twisting with simultaneous stretching. This stretch-twisting process has its limitations since more than a certain degree of twisting results in destruction of the structure of the material. The degree of twisting must therefore be limited and consequently an increase of the elastic limit of the rods beyond a certain value is impossible.

In accordance with the present invention the strength of reinforcing elements for concrete structures is considerably increased by rolling the rods between profiled rolls which subject the material of the rod to a kneading action whereby its bonding capacity is increased simultaneously. The rods of flattened cross section obtained by this process may then be subjected to the known twisting or stretch-twisting operation, or two or more of them may be twisted together with or without simultaneous stretching.

For the better understanding of the invention, reference is now made to the accompanying drawing, in which:

I the opposite direction;

Figures 4 and 5 are views similar to Figures 3 (c) and 3 (d), showing the result obtained with a modified rolling operation.

In carrying out the invention according to one embodiment thereof, the round section'iron or steel rod i shown in Figures 1 and 3 (a) is first subjected to a cold rolling operation between profiled rolls, whereby the rod is given the form shown in Figures 2 and 3 (b) the rod being. flattened in cross section and indentations 2 formed in the flat faces. These indentations may be-of an desired shape and disposition, but preferably they take the form of parallel notches, inclined to the axis of the rod and so disposed that no cross section of the rod is weakened by more than one of the notches on each side of the rod, all as shown in the drawing. The notches formed in the two opposite flat sides of the rod are oppositely inclined, so that they cross one another when the rod is viewed in elevation. In this cold rolling process the material of the rod is very considerably improved by the kneading action, particularly in the zones marked A in the Figure 2. The elastic limit of the reinforcing element produced is considerably higher than that of the initial round rod but does not possess the defects which would result from excessive twisting.

The strength of the cold rolled rod may be increased further by a twisting operation, with or without simultaneous stretching, without causing the formation of harmful cracks or the like. If the rod is twisted in the direction of the arrow I of Figure 3 (b) it assumes the shape shown in Figure 3 (d), while if it is twisted in the direction of the arrow II of Figure 3 (b) it assumes the shape shown in Figure 3 (c) In the former case the notches extend after twisting substantially perpendicularly to the helical line of the twisted outer fibres, while in the rod shown in Figure 3 (d) they extend substantially parallel to the helical line of the outer fibres. These two arrangements have various advantages, which are of importance in reinforced concrete construction. The reinforcing rod of Figure 3 (c) is distinguished by particularly good adhesive capacity,

.while that of Figure 3 (d) can resist stretching In carrying out the twisting operation upon the rods thus far described, care must be taken to see that the twisting takes place in the required direction and owingto the awkward nature of the work pieces some difliculty and loss of time may be experienced in presenting them to the twisting machine in the required position. For this reason it has been found preferable to modify the cold rolling process so that the inclined notches on the two opposite faces of the rod lie parallel to one another instead of crossing. Somewhat surprisingly it is found that such a rolling process does not cause bending of the rod to an extent greater than can subsequently be rectified by a trueing operation or by the twisting operation itself. when the rods are cold rolled in this manner, the same result is obtained whichever direction of twisting is adopted, as clearly appears from Figures 4 and 5, so that the rods may be fed to the twisting machine in the usual way. The twisted rods thus obtained comblue the advantages of the rods shown in Figures ,3 (c) and a (a).

In all cases, the twisting operation improves more particularly those zones which are not di rectly influenced by the cold rolling operation. This is due to the fact that as a result of the rolling operation the zones (A in Figure 2) partieularly influenced by the cold rolling are brought nearer to the axis of the rod. while the zones least influenced (B in Figure 2) are forced away from the axis and are consequently most affected by the twisting operation. Thus a greater increase of the elastic limit is obtained by a relatively small degree of twisting and cracks due to twisting are avoided. The twisting operation also results in an equalization of the strength over the whole length of the reinforc- 2. A method for the production of a reinforcing element for concrete structures which comprises cold rolling a metal rod to provide a series of the rod in the portions thereof least affected by the said cold rolling operation.

3. A, method for the production of a reinforcing element for concrete structures which comprises cold rolling a plurality of metal rods between opposing surfaces of profiled rolls to provide flattened opposite faces having parallel in' dentations therein and producing kneading ac-' ing rod, any variations of strength, which may be due to slight variations of the cross section, in the initial material being equalized. It is a particular advantage of the present invention that the strength (elastic limit) of the rods is improved much beyond that of the known stretch twisted reinforcing elements with a much smaller degree of twisting, i. e. without subjecting the rod to such high stresses. A further advantage is that the reinforcing rods of the present invention have excellent bonding capacity and in this respect are readily distinguishable from smooth surfaced rods.

Reinforcing members having very great bonding capacity may be obtained by twisting together, either with or without simultaneous stretching, two or more of the rods thus far de-. scribed. The rods used may be cold-rolled but untwisted rods as shown in Figures 2 and 3 (b) or rods which have themselves been twisted after cold-rolling as shown in Figures 3 (c), 3 (d), 4

distributed over the whole length of the beam.

I claim: f

1. A method for the production of a reinforcing element for concrete structures which comprises cold rolling a metal rod to alter the cross section thereof and to produce kneading action in the portions of the rod most affected by the cold rolling operation and thereafter cold twisting the rod to improve the tensile strength in the portions of the rod not directly affected by the said cold rolling operation, thereby greatly in-- creasing the tensile strength and elastic limit of the rod.

tion in the portions thereof most affected by the cold rolling operation, cold twisting a plurality of the rods together and simultaneously stretching the rods to increase the tensile strength thereof in the portions least affected by the said cold rolling operation, thereby improving the tensile strength, elastic limit and bonding capacity of the rods.

4. A method for the production of a reinforcing element for concrete structures which comprises cold rolling a round metal rod to provide a flattened cross section having indentations in the oppositely disposed surfaces thereof by means of profiled rolls having inclined parallel projections thereon, the projections on one roll crossing those of the other opposing roll, producing indentations .on opposite faces of the rod inclined at an angle to the helical line of the outer fibres thereof, the indentations on said opposite faces being in crossed relation and cold twisting the. said rod. Y

5. A method for the production of a reinforcing element for concrete structures which comprises cold rolling a metal rod to provide a flattened cross section by means of profiled rolls having inclined parallel projections on each roll, the projections on one roll crossing those of the opposite roll, producing a flattened cross section having parallel indentations on each of the faces thereof, and coldtwisting the rod so that the indentations on one face are inclined substantially at right angles to the helical line of the twisted outer fibres, while those on the other face extend substantially parallel to the helical line of the twisted outer fibres.

6. A method for the production of a reinforcing element for concrete structures which comprises cold rolling a plurality of metal rods to form a flattened cross section in each of the rods and producing a series of parallel notches in the flattened faces of the rods inclined to the axes thereof and thereafter cold twisting the rods together, to increase the tensile strength, bonding capacity and elastic limit of the rod.

. ERNST HOFFMANN. 

